This invention relates to a portable test instrument, and more particularly to a nuclear gauge for measuring the density properties of a test material.
Portable nuclear gauges are frequently used in the construction industry for measuring the moisture content and density of soils, soil-stone aggregates, cement, and asphalt. One such gauge which has been commercially available for a number of years is the 3400 Series surface moisture-density gauge manufactured by Troxler Electronic Laboratories of Research Triangle Park, N.C., the assignee of the present invention.
These gauges utilize the principle of Compton scattering of gamma rays for determining the density characteristics of the test material. The aforementioned type of gauge typically employs gamma radiation sources having an activity level in the millicurie range. For example, the Troxler 3400 Series moisture-density gauge employs a cesium-137 gamma source containing approximately eight millicurie of cesium-137.
Many jurisdictions impose regulations and licensing requirements with respect to the handling and use of nuclear test instruments with gamma radiation sources in the millicurie range. However, nuclear density gauges which use nuclear sources of relatively low activity, e.g. in the microcurie range are subject to fewer and less stringent restrictions and regulations. Gauges of this type are described, for example in U.S. Pat. Nos. 4,766,319 and 6,567,498, assigned to Troxler Electronic Laboratories of Research Triangle Park, N.C., the assignee of the present application.
It is an object of the present invention to provide improvements in a nuclear density gauge, and more particularly to a nuclear density gauge of the type which uses a low activity gamma radiation source.